body {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

main {
    flex: 1;
}

body {
    margin: 0;
    font: 100%/1.5 Baskerville, Palatino Linotype, Palatino, serif;
}

h1 {
    margin: .5em 0 0;
}

header {
    text-align: center;
    height: 3em;
}

main,
footer {
    display: block;
    padding: .5em calc(50% - 400px);
}

footer {
    background: linear-gradient(#222, #444);
    color: white;
}